Typewriter key cap switch for additional signals



A. w. HOLT 3,020,995

TYPEWRITER KEY CAP SWITCH FOR ADDITIONAL SIGNALS Feb. 13, 1962 Filed April 10, 1961 fl rnl n I INVENTOR Arthur W. Ho/f ATTORNEYJ 3,020,995 TYPEWRITER KEY CAP SWITCH FOR ADDITIONAL SIGNALS Arthur W. Holt, Silver Spring, Md., assiguor to Rabinow Engineering Co., Inc., Takoma Park, Md. Filed Apr. 10, 1961, Ser. No. 102,054 7 Claims. (Cl. 1971) This invention relates to typewriter attachments and more particularly to improvements in auxiliary equipment for standard or special typewriters.

I use the term typewriter in a general sense to include any kind of machine which prints or otherwise transmits or manifests information upon depression of keys. Examples are adding machines, cash registers, secretarial typewriters, accounting machines, etc.

I am aware of prior typewriter auxiliary equipment capable of preparing codes, records, etc., in response to depression of the keys of the typewriter. For instance, US. Patent No. 1,829,233 and US. Patent No. 2,745,532. These prior patents seem to be typical of the prior art, where equipment is operatively connected with the mechanism of the typewriter in order to generate codes or to perform other duties each time that a key is depressed. One of the drawbacks in the prior art is that the typewriter itself has to be modified quite extensively Inited States Patent Typewriter may be a fully mechanical typewriter, although it is to be understood that the principles of my invention are equally well applicable to the more modern electric typewriters, adding machines, etc., in accordance with the previous definition of the word typewriter. The

' utilization device 12 may be of any type, and therefore it is only schematically represented. It may provide code to make the auxiliary equipment operative. Possibly the simplest modification is disclosed in the E. L. Morss et al. patent which discloses a number of switches (plus other modifications) showing that they are operated by movement of the key levers. Even this small modification of an existing typewriter can be serious when there is not enough room provided in the manufacture of the typewriter.

Accordingly, an object of my invention is to provide auxiliary equipment for virtually any manufacturers make, modeland style of typewriter which will provide an electrical output, or at least control an electrical output, corresponding to the key which is depressed. The system which I have developed requires absolutely no struc tural alteration to the existing typewriter equipment. Instead, I furnish a group of typewriter key caps to fit over the keys of the typewriter, and a switching means associated with each cap. In some embodiments lightweight, flexible conductors are operatively connected with the key cap-mounted switches, and these are properly connected in the circuits of a utilization device, such as a code generator, display, etc.

A further object of my invention is to provide auxiliary equipment for the typewriter, which does not in any way interfere with the mechanical or electrical internal operating system of the typewriter, and yet reliably provides output signals corresponding to the depressed key or keys. The signals may be used for any purpose whatsoever.

Other objects and features of importance will become evident in following the description of the illustrated forms of the invention.

FIGURE 1 is a partially perspective and partially elevational view of the conventional typewriter equipped with auxiliary equipment exemplifying the invention.

FIGURE 2 is a fragmentary perspective view showing two conventional key levers having my key caps thereon.

FIGURE 3 is an enlarged sectional view taken on line 3--3 of FIGURE 2.

FIGURE 3a is a sectional view on an enlarged scale and taken on line 3a3a of FIGURE 3.

FIGURE 4 is an exloded perspective view of a modification.

FIGURE 5 is a perspective view of another modification.

FIGURE 6 is a perspective view of a further modification.

outputs, analog character identification outputs, display outputs, etc. In, each case, it is preferred that the device 12 be electrically operative and therefore I have shown electrical source 14 (FIGURE 2) between my key caps 16, 18 and device 12; In the embodiment of FIG- URE 5 the device 12a is an R. F. generator, while FIG- URE 6 discloses device 12b as a capacitance proximity circuit.

Typical key cap 16 (FIGURE 3) is fitted over key 20 at the outer end of the key lever 22. The key and key lever are conventional and unaltered by the presence of key cap 16. structurally, the key cap embodies a switch 24 which is closed upon intial depression of the key 20. Switch 24 is made quite sensitive. One embodiment has cap 16 made of an annular flexible plastic, e.g. polyethylene, side Wall or skirt 26 fitting around the edges of the key 20 and frictionally held in place. The top wall 28 of the key cap is curved, and both flexible and elastic. A thin contact 30 is secured to the inner surface of the cap wall 28, for instance, by cementing, by fastener 29, or by any other suitable means. Its normal position is slightly spaced from a contact formed as a transverse wall 32 snapped in a groove 34 near the upper edge of wall 26, and frictionally held in place or otherwise fastened. Conductors 36 and 38 are attached to contacts 30 and 32 respectively, and they form a part of the cricuit network 40 operatively connecting the key caps with device 12. Alternatively, one conductor instead of a pair may be used, in which case the typewriter will be used as an electrical ground. The use of the key caps shown in FIGURE 3 is now deemed evident. As the typist applies a force to depress key 20, the flexible Wall 28 defiects downwardly causing the contacts 30 and 32 to touch thereby closing one of the circuits of or otherwise operating device 12. Additional force in a downward direction causes the key 20 to be depressed for its normal duty cycle. As soon as the typist relieves the force from the wall 28, the inherent elasticity and resilience of the wall 28 restores it to its original position, i.e. the switch-open position.

Each form (FIGURES 3-6) of key cap may use similar Wiring. A single wiring harness containing a group of flat' ribbon conductors 40 is supplied. At one end there is a connection to the utilization device 12 and at the other end the wires are arranged in pairs but housed within individual flat, lightweight, highly flexible insulation bodies 48 (FIGURE 3a). For initial installation, the conductors may be wrapped around the individual key levers, or left free, or they may be adhered to portions of the key levers as shown in FIGURE 3a. In the latter alternative, a pressure-sensitive adhesive is provided on one surface of fiat ribbon conductors 48. This may be protected by a peel-off strip which is removed at the time of installation. After removal the ribbon conductor is pressed against a face of the key lever, and the adhesive substance will hold it in place.

FIGURE 4 shows a modification of my key cap. The key cap 50 is composed of a housing 52 whose side wall is shaped to conform to the configuration of a conventional typewriter key. The essential difference between the embodiment of FIGURE 4 and that of FIGURE 3 is in the switch construction. conductive disc 56 which is similar to contact 32, and the upper end of housing 52 is open. Spring member 58,

Patented Feb. 13, 1962 Switch 54 is made of a Y for instance a thin, flexible sponge Washer, is disposed on contact 56, holding the upper moveable contact 60 normally spaced therefrom. The upper contact 60 is in the form of a copperclad plastic disc or simply a metal disc fitted under the upper flange 62 of housing 52. The conductors attached to contacts 60 and 56 are the same as the conductors 36 and 38. When the key cap 59 is depressed, the switch is closed by movement of the contact 60 into engagement with the raised part 57 of contact 56 against the yielding opposition of the insulating resilient member 58.

FIGURE 5 discloses a key cap 70 which difiers from the others in the switch construction and energy source. Instead of a mechanical switch, I disclose a coil 72 embedded in or otherwise attached to the upper wall of the key cap housing. As the operator brings his or her finger very close to the coil, the R.F. field is altered thereby causing the R35. utilization device 12a to provide an output signal.

FIGURE 6 shows key cap 78 which is quite similar to key cap 70. The difierence is that the proximity utilization device 12b is a high impedance, capacitance operated circuit network. Therefore, switch 80 is a capacitor plate embedded in or otherwise connected with the top Wall of the key cap housing. While the forms of my invention shown in FIGURES 1-4 may be used with any typewriter, the forms shown in FIGURES 5 and 6 are better suited for apparatus where the operator is not accustomed to keep his fingers on the keys. An adding machine would be a good example of apparatus where the key caps of FIGURES 5 and 6 would be used.

It is understood that various changes, and alterations may be made in this invention without departing from the scope of the following claims.

I claim:

1. In a typewriter which has keys, an apparatus to print in response to depression of the keys, auxiliary equipment to provide an output signal corresponding to the keys which are depressed, said equipment including a code generator, circuit conductors extending from said generator, means connected with said conductors for operating said code generator and including a structural device attached to each key so that upon operation of the key said structural device is first contacted by the typist.

2. The subject matter of claim 1 wherein said structural device includes a switch.

3. The subject matter of claim 1 wherein said device is a proximity switch.

4. Subject matter of claim 1 wherein said device is a mechanical switch.

5. For use with any of a plurality of conventional type writers, each of which has keys supported by key levers that are moved when the keys are depressed to cause the typewriter to operate, the improvement comprising a separate assembly forming an attachment capable of being connected to the typewriter while requiring no substantial modification of the existing structure of the typewriter, said assembly comprising a utilization device to provide output signals corresponding to each key of the typewriter, a plurality of conductors extending from said utilization device, a key cap for each key, and a switch incorporated in each key cap, said conductors operatively connected with respective key cap switches to operate said utilization device in accordance with the particular key which is depressed.

6. The subject matter of claim 5 wherein said conductors have an adhesive substance thereon holding portions of said conductors to said key levers.

7. For use with the combination of a utilization device and a typewriter having keys, a separate attachment for the typewriter which operates said utilization device in accordance with the particular typewriter keys that are depressed, said attachment including key caps for the keys which constitute the sole necessary mechanical connection with the typewriter thereby being independent of all mechanical motions within the typewriter itself, switch means associated with each key cap, and electrical conductors connecting said switch means with said utilization device.

Tompkins Oct. 26, 1909 Netherlands May 16, 1961 

